The advent of horizontal drilling has been considered a significant advance in the oil and gas industry. While this form of drilling has increased the complexity and cost of drilling, it has also increased economic returns to well operators. Horizontal drilling has lead to increased production because it maximizes the reservoir contact. This is because most oil and gas fields are generally horizontally situated. It has also enabled tapping reserves from zones previously thought too difficult to reach, such as thin oil zones.
Although horizontal completion technology and techniques have improved over the years, horizontal wells continue to face challenges. One of those challenges relates to uneven influx of reservoir fluid to the wellbore. This causes early water and gas breakthrough. Water and gas coning in the heel of the well is often blamed for these challenges. Another reason for water and gas breakthrough is related to uneven permeability and fractures or differences in fluid mobility, which occurs in wells with high-viscosity oil. Since it becomes easier for the reservoir fluid to be produced through one section compared to the other, having an even drawdown under conditions of uneven permeability or uneven fluid mobility can lead to premature breakthrough of water or gas.
In reservoirs which are largely homogenous with higher drawdown in the heel, one solution to the challenge of water and gas breakthrough is to balance the drawdown from the heel to the toe. This can be done by applying a controlled pressure drop from the annulus to the production tubing in the heel using inflow control devices (ICDs). The use of these devices reduces the drawdown and the fluid rate from this particular section. In reservoirs which are mostly heterogenous, where the drawdown is more equally distributed along the wellbore, the drawdown is reduced in high-permeability sections to allow low-productivity sections to flow more oil. This is typically achieved through equal distribution of the ICDs. ICDs have thus been very effective at delaying potential water or gas breakthroughs and thus allowing more oil to be produced throughout the life of the well.
There are some instances, however, where the balancing achieved using ICDs is insufficient to delay water and gas coning at the heel of a well. In those instances, it is desirable to close these zones at the heel while still allowing production from the deeper zones.